W77IE58 Datasheet, PDF (45/90 Pages) Winbond – 8-BIT MICROCONTROLLER

Preliminary W77IE58
Machine cycles in standard 8032 = 10 + (26 * CNT)
Machine cycles in W77IE58 = 10 + (26 * CNT)
If CNT = 50
Clock cycles in standard 8032= ((10 + (26 *50)) * 12 = (10 + 1300) * 12 = 15720
Clock cycles in W77IE58 = ((10 + (26 * 50)) * 4 = (10 + 1300) * 4 = 5240
Block Move with Two Data Pointers in W77IE58:
; SH and SL are the high and low bytes of Source Address
; DH and DL are the high and low bytes of Destination Address
; CNT is the number of bytes to be moved
MOV R2, #CNT
MOV DPS, #00h
MOV DPTR, #DHDL
INC DPS
MOV DPTR, #SHSL
LOOP:
MOVX A, @DPTR
INC DPTR
DEC DPS
MOVX @DPTR, A
INC DPTR
INC DPS
DJNZ R2, LOOP
; Load R2 with the count value
; Clear DPS to point to DPTR
; Load DPTR with Destination address
; Set DPS to point to DPTR1
; Load DPTR1 with Source address
; Get data from Source block
; Increment source address
; Clear DPS to point to DPTR
; Write data to Destination
; Increment destination address
; Set DPS to point to DPTR1
; Check if all done
Machine cycles of W77IE58
#
2
2
3
2
3
2
2
2
2
2
2
3
Machine cycles in W77IE58 = 12 + (15 * CNT)
If CNT = 50
Clock cycles in W77IE58 = (12 + (15 * 50)) * 4 = (12 + 750) * 4 = 3048
We can see that in the first program the standard 8032 takes 15720 cycles, while the W77IE58 takes
only 5240 cycles for the same code. In the second program, written for the W77IE58, program execution
requires only 3048 clock cycles. If the size of the block is increased then the saving is even greater.
External Data Memory Access Timing
The timing for the MOVX instruction is another feature of the W77IE58. In the standard 8032, the MOVX
instruction has a fixed execution time of 2 machine cycles. However in the W77IE58, the duration of the
access can be varied by the user.
The instruction starts off as a normal op-code fetch of 4 clocks. In the next machine cycle, the W77IE58
puts out the address of the external Data Memory and the actual access occurs here. The user can
change the duration of this access time by setting the STRETCH value. The Clock Control SFR
(CKCON) has three bits that control the stretch value. These three bits are M2-0 (bits 2-0 of CKCON).
These three bits give the user 8 different access time options. The stretch can be varied from 0 to 7,
resulting in MOVX instructions that last from 2 to 9 machine cycles in length. Note that the stretching of
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Publication Release Date: July 2000
Revision A1